A boiler making noise can be caused by trapped air, limescale, low pressure, circulation problems or worn components. Learn what different boiler sounds may mean and when professional help is needed.
A boiler will normally make some sound while heating your home or producing hot water. Pumps operate, water circulates through pipes and components expand slightly as they warm up.
However, a boiler that suddenly starts banging, gurgling, whistling, buzzing or vibrating may be telling you that something in the heating system is no longer working as it should.
Some boiler noises have relatively simple causes, while others can point to circulation problems, scale build-up, a faulty pump or components inside the boiler that require professional attention.
The type of sound, when it happens and whether your heating or hot water is also affected can provide useful clues.
Is a Noisy Boiler Always a Problem?
Common Boiler Noises and What They Mean
What You Can Safely Check Yourself
Why a Boiler Makes Noise When Heating Starts
Can Low Boiler Pressure Cause Noise?
When Should You Turn the Boiler Off?
When to Call a Gas Safe Engineer
Preventing Boiler Noise
Boiler Repairs & Diagnostics in London
Frequently Asked Questions
Not every sound coming from a boiler means that it is about to break down.
A quiet hum while the boiler is operating, gentle water movement through the system or occasional clicking as pipes warm and cool can be normal.
The important thing is to notice changes in the way your boiler sounds.
A new sound that becomes noticeably louder, continues for longer than usual or appears together with other symptoms should be investigated.
These symptoms may include:
Radiators taking longer to heat
Some radiators remaining cold
Boiler pressure dropping
Boiler repeatedly switching itself off
Hot water changing temperature
Fault codes appearing on the display
Water leaking around the boiler
Heating becoming unusually noisy
If the boiler is otherwise operating normally, the sound may originate elsewhere in the central heating system rather than from the boiler itself.
Different sounds can point towards different parts of the heating system.
Loud banging can sometimes happen when water circulation through the heating system is restricted.
Possible causes include:
Trapped air
Sludge or debris in the heating system
Scale deposits
A circulation problem
Pump problems
Pipes expanding or moving
Internal boiler components operating incorrectly
If banging appears suddenly and is coming directly from inside the boiler, it should not simply be ignored.
A heating engineer can determine whether the noise is caused by the boiler itself or by the connected pipework and radiators.
Gurgling is often associated with water and air moving through the heating system.
You may also hear similar sounds from radiators.
Common causes can include:
Air trapped inside radiators
Low system pressure
Poor circulation
Water moving through partially restricted pipework
A circulation pump problem
If one or more radiators are cold at the top while making gurgling sounds, trapped air may be contributing to the problem.
However, persistent gurgling from inside the boiler itself may require further investigation.
A high-pitched whistling sound is often described as boiler kettling because it can sound similar to a kettle heating water.
Kettling can occur when water does not move through the boiler as freely as it should.
Scale, sludge or another restriction can cause water around the heat exchanger to become hotter than intended.
This does not necessarily mean the boiler needs replacing, but repeated kettling should be investigated because poor circulation can place additional strain on the heating system.
A low humming sound can be normal while the boiler pump or fan is operating.
A much louder humming, buzzing or electrical-type noise may indicate that a component is working harder than normal.
Possible causes include:
Pump problems
Fan issues
Electrical components
Vibrating internal parts
Restricted water circulation
Do not remove the boiler casing or attempt to investigate internal electrical or gas components yourself.
Vibration can sometimes come from the boiler itself, but it may also travel through nearby pipes and make the sound appear louder.
Possible causes include:
Loose pipework
A pump operating incorrectly
Fan problems
Components vibrating against the boiler casing
Poor circulation
The exact source can be difficult to identify because vibrations travel easily through walls, floors and heating pipes.
Occasional clicking when a heating system starts or stops can simply be caused by metal pipes expanding as their temperature changes.
Repeated clicking directly from the boiler may have a different cause.
Possible issues can include:
Ignition attempts
Heating controls
Valves operating
Pump operation
Internal boiler components
If the boiler repeatedly clicks but fails to start, professional diagnosis may be required.
A gentle whooshing sound may simply be water moving through the system.
If it becomes unusually loud, it can indicate that water is circulating at an unsuitable rate or that a valve, pump or other part of the heating system needs adjustment.
It is particularly worth investigating if the noise appears together with uneven radiator temperatures or changes in boiler performance.
There are several basic checks you can make without opening the boiler or touching gas-related components.
Look at the pressure gauge or digital display.
If pressure is significantly below the range recommended by the boiler manufacturer, circulation and boiler operation may be affected.
If your pressure keeps falling after being restored, read our guide Why Is My Boiler Losing Pressure? Causes & Solutions.
Look for:
Warning symbols
Fault codes
Low-pressure warnings
Reset notifications
Write down any fault code before resetting the boiler because it may help identify the problem later.
Listen to where the noise is actually coming from.
A sound that appears to come from the boiler may actually be travelling through the central heating pipework.
Check whether radiators:
Heat evenly
Have cold areas
Make gurgling sounds
Have visible leaks
Remain cold while others become hot
Make sure:
Heating is switched on
The thermostat is set above the current room temperature
Timer settings are correct
Wireless thermostat batteries are working
Smart heating controls are connected
Without removing any boiler panels, look around:
The boiler
Visible heating pipes
Radiator valves
Radiators
Water loss can cause boiler pressure and circulation problems.
A recurring leak should be professionally investigated rather than repeatedly topping up the system.
If the noise occurs mainly when central heating starts, it may be connected with water beginning to circulate through the system.
Cold pipes and radiators gradually warm and expand, which can cause occasional clicking or tapping.
More noticeable banging, gurgling or vibration can point towards issues such as:
Air in the system
Restricted circulation
Sludge
Pump problems
Pipe movement
Valves opening or closing incorrectly
The timing of the noise is useful information.
For example, tell your heating engineer whether it happens immediately when the boiler starts, after several minutes or only when the system reaches a higher temperature.
Low pressure can contribute to circulation problems and may sometimes appear together with gurgling or other unusual heating system noises.
The pressure should normally remain within the range recommended for your particular boiler.
If the pressure repeatedly drops, there may be another problem such as a leak, pressure-related component fault or issue elsewhere in the heating system.
Repeatedly repressurising a boiler without finding out why the pressure is falling is not a long-term solution.
For more information, see Why Is My Boiler Losing Pressure? Causes & Solutions.
A minor new sound does not automatically mean you need to immediately shut down the heating system.
However, you should stop using the boiler and seek professional advice if there are signs of a potentially serious problem.
These can include:
A smell of gas
Suspected carbon monoxide
A burning smell
Significant water leaking from the boiler
Very loud or violent banging
The boiler repeatedly shutting down
Electrical burning or unusual electrical noises
Warning signs that suggest unsafe operation
If you smell gas or suspect carbon monoxide, treat the situation as a gas emergency and contact the appropriate emergency service immediately.
Never remove the boiler casing or attempt to repair gas components yourself.
Contact a Gas Safe registered engineer if:
The boiler noise has suddenly become much louder
Banging or kettling continues
The boiler repeatedly switches itself off
You have no heating or hot water
Pressure repeatedly drops
A fault code keeps returning
Water is leaking from the boiler
The boiler is vibrating excessively
You suspect a pump, fan or internal component fault
Basic external checks have not identified the problem
Gas boilers contain components that should only be inspected and repaired by appropriately qualified professionals.
If the boiler has stopped working altogether, see our guide Boiler Not Working? Common Boiler Problems Explained.
Not every boiler problem can be prevented, particularly as components become older.
However, regular maintenance can help identify developing problems before they cause a complete breakdown.
Useful steps include:
Arrange regular boiler servicing
Investigate recurring pressure loss
Have persistent radiator problems checked
Deal with visible leaks promptly
Keep the heating system maintained
Do not ignore new or increasingly loud boiler noises
Have circulation or sludge problems professionally assessed
Heating systems work as a complete circuit.
A problem with radiators, pipework, pumps or system water can eventually affect boiler performance as well.
If your boiler is banging, gurgling, whistling, buzzing or making another unusual sound, the first step is identifying where the noise originates.
TES Heating provides boiler diagnostics and boiler repairs across London, checking the boiler and connected heating system to determine what is causing the problem.
The investigation can include checking:
Boiler operation
System pressure
Heating circulation
Radiators
Pumps and controls
Visible leaks
Fault codes
Heating system performance
Once the likely cause has been identified, the appropriate repair or maintenance can be recommended.
Gas-related boiler work is carried out by a Gas Safe registered engineer.
For other plumbing and heating work, see Plumbing & Heating Services London.
A new loud boiler noise can have several causes, including trapped air, restricted circulation, scale, sludge, a pump problem or another component fault. The type and timing of the noise can help identify the likely cause.
Not every banging sound indicates an immediate danger, but persistent or unusually loud banging should be investigated. If there is also leaking water, a gas smell, burning smell or repeated boiler shutdown, stop using the boiler and seek professional advice.
Gurgling is often associated with air or water moving through the heating system. Trapped air, low pressure or circulation problems can all contribute to the sound.
Boiler kettling is commonly described as a whistling, rumbling or kettle-like sound. It can occur when water circulation through the boiler is restricted.
You can safely check external controls, boiler pressure, fault codes, radiators and visible leaks. You should not remove the boiler casing or attempt repairs to gas, combustion or internal electrical components. Those should be checked by a Gas Safe registered engineer.
